This invention relates to the utilization of chemiluminescent reactions, and, more particularly, to the presentation format for reactants useful in chemiluminescent reactions.
In several types of chemical and medical test procedures, a liquid such as a food product or a body fluid must be reacted with individual reactants in a sequence of related but separate chemical reactions, and then the final product analyzed. Traditionally, such procedures have been performed by placing the fluid into a reaction tube or the like, adding the remaining reactants for the first reaction, and permitting the first reaction to proceed to completion. The further reactants for the second reaction are added, and the second reaction is permitted to proceed to completion. This stepwise operation can be repeated as many times as necessary, until a final reaction product is obtained for analysis. This technique is not particularly suitable for conducting measurements of reaction such as those that produce measurable light by chemiluminescence, because of the time required to conduct the final mixing and place the reaction tube into a light-measurement apparatus.
In an alternative approach better suited for the measurement of chemiluminescent reactions, a plastic test plate having multichambered test wells has been developed. A liquid test sample is placed into a sample receiving chamber, which has a sloping wall, and mixed with reactants previously placed into the first chamber. The test plate is tilted so that the mixture flows along the sloping wall of the sample receiving chamber and into a reaction measurement chamber. The reaction measurement chamber is preferably cylindrical in shape with a flat bottom that is pressed against a piece of photographic film. The mixture from the sample receiving chamber mixes with additional reactants and the light-producing reaction occurs if the original test sample contained a chemical under test. The intensity of any resulting light is measured through the transparent flat bottom of the reaction measurement chamber. The apparatus for conducting such testing is disclosed in U.S. Pat. No. 4,985,631.
The light intensity produced by many chemiluminescent reactions of interest is quite low, and a continuing problem has been the most efficient utilization of the light produced in the test well. Very sensitive (fast) film can be used to record the light. A number of light intensifying techniques have been used. Various geometries of the test well have been tried, in an effort to concentrate the light onto the film.
A related problem is the stability of the reagents stored in the well. In one highly sensitive form of chemiluminescence, luciferin and luciferase are reacted together with adenosine triphosphate (ATP) to produce light. The ATP is normally provided from the test specimen by a chemical release sequence that is operable only to release ATP under carefully selected circumstances. The luciferin and luciferase are provided in the test well, and there react with the ATP, if any, released from the test sample.
The chemiluminescent reagent luciferase has a relatively short period of full activity after preparation. After a few hours, the activity or reactive strength of the luciferase begins to deteriorate. The result of this deterioration is that the maximum light output of the chemiluminescent reaction, once it occurs, also is less than for freshly prepared luciferase. With prolonged storage, the luciferase becomes so weak that the light output is insufficient for exposure of the film, and the testing procedure becomes inoperable. Luciferase can be stored at reduced temperatures to prolong its active life, but for many applications such as remote sites or clinics, reduced temperature storage is not feasible or inconvenient.
Thus, the viability of chemiluminescent testing often can be linked to the potential light intensity of the reaction, and thence to the loss of that potential as a result of deterioration during storage of the reagents. There is a continuing need for improved techniques for improving the light intensity of the reaction, and retaining that maximum intensity even with prolonged storage of the reagents. The present invention fulfills this need, and further provides related advantages.